Converted vec2 to a template class
Implemented default scalar (float) and optional double scalar in math
Moved math::quantity to qty::quantity
Renamed vec2.cpp in test to test_vec2.cpp to match convention
Fixed template arguments in base_unit classes for qty
vector2 renamed to vec2_t for the new template convention
Implemented math::vec3
Implemented cross product
Implemented math::vec4
Implemented degrees and radians for math